How HERS Ratings and the Florida Energy Code Shape a Custom Home in St. Petersburg

If you are planning a custom home in St. Pete, energy efficiency is not just marketing copy. It is a code requirement, a measurable score on your finished house, and one of the few construction decisions where every dollar spent up front returns money on your power bill every month for as long as you own the home. This piece walks through what the Florida Energy Code actually requires, what a HERS rating means, and where it makes sense to build beyond the code minimum in Florida climate zone 2.

What is a HERS rating on a custom home?

HERS stands for Home Energy Rating System. It is a scored energy-performance benchmark developed and maintained by RESNET, the Residential Energy Services Network — the industry body that publishes the standard, credentials the raters, and certifies the software the ratings run through.

A HERS Index score is a single number that compares your finished custom home against a reference home of the same size, shape, and layout built exactly to a fixed baseline of the 2006 International Energy Conservation Code. The reference home is scored at 100. Lower is better.

• A HERS 100 house uses the same energy as the reference baseline.
• A HERS 70 house uses roughly 30 percent less energy than the reference.
• A HERS 0 house is net-zero — it produces as much energy as it consumes over the year.
• A negative HERS score means the house produces more energy than it consumes.

On a Florida climate zone 2 custom home built to current code, HERS scores commonly land somewhere in the 60s or 70s before any beyond-code upgrades. That is because code has tightened meaningfully every three-year cycle since the 2006 reference year.

Does a Florida custom home have to have a HERS rating?

Not always. The Florida Energy Conservation Code, which is part of the Florida Building Code, gives builders two compliance pathways: the prescriptive path and the performance path (typically referenced as R405 in the residential energy provisions).

• Prescriptive path — the builder hits every minimum insulation R-value, window SHGC, duct-leakage threshold, and equipment efficiency the code lists, item by item. No HERS rating required.
• Performance path (R405) — the builder models the whole-house energy use in approved software and shows total annual energy cost is at or below the reference. This path is what actually produces the HERS rating, because the modeling software and the rating software share the same underlying methodology.

Custom homes with any real design ambition — vaulted ceilings, expansive glass, unusual roof geometry, oversized sliders — almost always end up on the performance path. The prescriptive path is too rigid to absorb design trade-offs, so the builder trades window area against wall insulation, or upgraded HVAC against duct sealing, and models the whole envelope in R405 software.

What does the Florida Energy Code actually regulate in a custom home?

The current Florida Energy Conservation Code sets minimum performance thresholds across five main envelope and systems categories:

• Ceiling, wall, and floor insulation — minimum R-values by assembly type, adjusted for climate zone. Pinellas County is climate zone 2, one of the mildest cooling-load zones nationally.
• Fenestration — maximum U-factor and maximum solar heat gain coefficient (SHGC) on windows, skylights, and glass doors. SHGC matters more than U-factor in Florida because we are fighting solar gain, not conducted heat loss.
• Duct sealing and testing — total duct leakage must be verified by pressure test after installation. Duct leakage is the single most consequential efficiency variable in a hot-humid climate because leaky ducts pull humid attic air into the conditioned space.
• Envelope tightness — whole-house air leakage measured by blower door test at final. Tighter envelopes mean less humid outside air infiltrating, which the HVAC has to dehumidify.
• HVAC and water heating equipment efficiency — minimum SEER2 and HSPF2 ratings on cooling and heating equipment, and UEF minimums on water heaters.

Specific R-values, SHGC caps, and duct-leakage thresholds change every code cycle. Your builder should be referencing the current code chapter directly at permit time rather than working from a prior-cycle number that may have moved.

Can we build beyond the Florida Energy Code?

Yes. Jeremy, one of Revolution’s owners, put it this way in a recent interview about custom-home cost drivers:

“We are bound under current code on what we’re allowed to do in terms of insulation, but that can always be exceeded for someone that wants to be more environmentally conscious.”

That framing — code as a floor, not a ceiling — is the right one. Every category the code regulates has an upgrade path that raises up-front cost and lowers HERS score and lifetime operating cost. The trade-off is not whether to build beyond code, but which upgrades give the highest return on your specific lot, orientation, and design.

Common beyond-code upgrades on Florida climate zone 2 custom homes:

• Spray foam insulation in unvented attic assemblies instead of blow-in batts in vented attics, which pulls the entire HVAC and duct system inside the conditioned envelope and typically drops duct leakage to near zero.
• Continuous exterior rigid insulation on wall assemblies to break thermal bridging at studs.
• Impact windows with SHGC in the low 0.20s instead of the code maximum.
• Right-sized higher-SEER2 variable-speed HVAC with dedicated dehumidification instead of the smallest allowable code-minimum unit.
• Heat-pump water heaters instead of standard electric resistance.
• Roof-mounted solar sized to hit a target HERS score with rebate.

What is the ROI on a lower HERS score in a Florida custom home?

The honest answer is that ROI depends on your utility rates, how long you plan to own the house, how you finance the upgrades, and whether you value comfort and humidity control as much as the dollar savings. RESNET publishes methodology but does not publish universal dollar ROIs, and no reputable custom builder should either.

What is defensible:

• Every point drop in HERS score reflects a measurable reduction in modeled annual energy use.
• Beyond-code envelope and duct-sealing upgrades tend to have the shortest payback in Florida because our cooling season is long and our humidity load is unforgiving.
• Solar has the most variable payback because it depends heavily on utility net-metering policy, which shifts.

If you want a real ROI on your specific build, the R405 energy model your builder runs for permit compliance can be re-run with each upgrade layered on. That gives you a modeled annual-energy-cost delta for every trade-off. Ask for it.

Who orders the HERS rating on a custom home?

Usually the builder does, when the design is on the performance path. A certified HERS Rater is an independent third party accredited by RESNET; they run the energy model at permit stage, perform the blower door test and duct leakage test at final, and issue the HERS certificate that gets recorded with the permit closeout.

The rater’s fee is folded into the general contract, and the rating itself becomes part of the house’s documentation package at closing. It also matters on resale — a HERS certificate is a defensible energy-performance disclosure that appraisers and future buyers can compare against other homes.

What questions should I ask my custom builder about energy code?

• Which compliance pathway — prescriptive or R405 performance — do you plan to file with?
• Who is your HERS Rater, and can you share their credentials?
• What HERS score does your typical custom home hit before any beyond-code upgrades?
• Where do you think the highest-return beyond-code upgrade is on my specific lot and design?
• Can I see the energy model output for the base design and a beyond-code version so I can compare?

Frequently Asked Questions

Next step

If you are early in planning a custom home in St. Pete and want to talk through where your specific design falls on the prescriptive vs performance pathway, or where the highest-return beyond-code upgrade lives for your lot, get in touch. Every custom-home estimate we build includes a conversation about which envelope and equipment decisions are worth spending on and which are diminishing returns.

Call (727) 888-6161 or use the contact form to start a conversation with Revolution Contractors — Jeremy, Thad, and the team have been building custom homes in Pinellas since 2016.

Related Resources:

• Custom home construction services — the hub for Revolution custom home work
• 2026 Florida Building Code changes — the code-cycle context that shapes energy provisions
• Custom home cost guide (St. Pete) — scope, contingency, and budget structure
• Custom home warranty (Florida) — what’s covered, for how long, by whom
• Custom home building process — step-by-step from lot to move-in